The aim of the study is to investigate the effects of ingesting glucose during five bouts of resistance exercise on muscle biological charateristics in m. vastus lateralis of moderately trained healthy individuals (20-45 years of age, n=20)

Muscular responses to resistance training vary extensively between humans, with many showing impaired growth. In such individuals, cellular plasticity is compromised, leading to reduced functional and health-beneficial outcomes of training. While this is likely due to a range of determinants, including epigenetic, genetic and physiological variables, recent studies suggest that it involves reduced ability to produce novel ribosomes in response to training. This eventually leads to less pronounced increases in protein synthesis, and thus decreased growth rates, and makes ribosomal content in muscle a potential proxy marker for training-associated muscle hypertrophy.

In a recent study, the investigators showed that increased resistance training volume was associated with more pronounced muscle growth, a trait that was associated with increased ribosomal biogenesis. Despite this, ~50 % of the participants did not exhibit true beneficial effects of increased training volume, which in turn coincided with reduced abilities to accumulate ribosomes. In such individuals, other means are likely necessary to circumvent the negative influence of genetic and epigenetic predispositions on muscle plasticity. Nutrient supplementation stand out as a potential therapy. However, at present, knowledge with regard to this perspective is limited to a selected few nutrients, with protein ingestion being the best studied potential adjuvant, for which adequate intake seems to be essential for achieving optimal muscle growth, potentially being interconnected with ribosomal synthesis. For other nutrients, such as glucose, little is know about their importance for muscle plasticity and ribosomal biogenesis.

In cell types such as cultivated kidney cells, exposure to high levels of glucose is an efficient mean to increase ribosomal biogenesis (and growth rates). This suggests that glucose is an important signaling molecule for increasing ribosomal production per se, perhaps acting as a ligand for signaling proteins or by acting to increase energy availability. In the human body (as opposed to cultured cells), glucose may also exert growth-stimulating effects by increasing insulin levels in blood. Overall, it thus seems plausible that glucose intake during resistance training may stimulate ribosomal biogenesis, in turn having beneficial effects for protein synthesis and muscle plasticity, perhaps acting in an additive manner to protein supplementation. At present, we do not know if this is the case, though studies have suggested that glucose ingestion during acute resistance training sessions may reduce training-induced muscle damage without affecting within-session work output (i.e. volume). This lack of knowledge is surprising given the long-standing appreciation of the beneficial effects of glucose intake for endurance performance, acting to delay muscular fatigue.

Inclusion Criteria:

• Non-smoking
• Moderately trained (i.e. having performed 2-8 resistance training sessions per 14 days for the last six months)

Exclusion Criteria:

• Not able to understand Norwegian
• Unstable cardiovascular disease
• Illness or injury contradicting heavy strength training
• Disabling musculoskeletal disease
• Serious mental illness
• Allergy to local anaesthesia
• Impaired glucose tolerance

On each intervention day, participants will receive boluses of supplements in accordance with his or her study ID number. The list that links this ID number to the randomization code will be kept with the person who generated the randomization code (and stored on a safe server) until completion of data sampling and cleaning of data on main outcome measures. The person resonsible for generating the randomization code will not be involved in any aspects of data sampling or handling. None of the project collaborators/participants will have access to this list during the intervention or during data handling.

Half the participants (n=10) will commence the intervention with GLU on Day 1, while the other half will commence with PLAC (randomized). For participants starting with GLU, half will perform training on their dominant leg, while the other half will perform training on their non-dominant leg. The same will be the case for participants starting with PLAC.